Electric Drive Unit Overload Protection for Trailer Steady
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Solution Overview
Problem
Electrically operated corner steadies for trailer vehicles often experience nut sticking on the spindle due to high friction at extreme positions, leading to motor failure, and existing solutions like overload protection result in prolonged operational times when moving support legs.
Innovation Solution
A control system with a control device inserted between the gearbox output shaft and spindle, featuring switching means that interrupt power supply when torque exceeds a predetermined value, allowing for higher speed operation without nut sticking, and includes resilient means to counteract non-critical loads and rectifier diodes for reversing spindle rotation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If continuous power is supplied to the motor at high speed, then operational speed is improved, but the nut gets stuck on the spindle due to high friction at extreme positions
Solution Approach 1:
The control device interrupts power supply to the motor before the nut reaches the extreme position where friction would cause it to stick. By detecting approaching extreme positions and preemptively stopping power supply, the system prevents the harmful high-friction condition from developing, allowing high-speed operation without the risk of nut sticking.
2Reliability
If overload protection is provided with low rotational speed, then motor protection is improved, but the time to move support leg is extended
Solution Approach 1:
The control device detects approaching extreme positions and interrupts power supply before the nut reaches the position where it would stick due to friction. This preliminary action prevents the need for slow-speed overload protection mechanisms, allowing the motor to operate at high speed throughout the entire stroke while still protecting against overload conditions.
3Force
If high torque is applied to overcome friction at extreme positions, then the nut can be released from sticking, but the motor experiences overload and may fail
Solution Approach 1:
The control device interrupts power supply to the motor before the nut reaches extreme positions where friction would cause sticking. By preventing the nut from reaching these positions in the first place, the system eliminates the need to apply high torque to overcome friction, thereby protecting the motor from overload conditions that would otherwise be necessary to resolve sticking.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables faster operation of support legs without nut sticking and motor failure, while maintaining protection against overload and frictional locking, allowing for efficient leveling of trailer vehicles on uneven ground.
Implementation Method 1
a steep rise in torque in the spindle due to the power characteristic of the electric motor
Implementation Method 2
the friction between nut and spindle may become so high that nut will get stuck on the thread of the spindle
Implementation Method 3
resilient means to counteract non-critical loads
Data Source
AI summary
An overload protection in a drive unit for a steady or jack for a caravan comprises an electro-mechanical control system. A spindle is driven by a motor through a gearbox, wherein the motor is controlled through a power supply. A control device in the system comprises a movable part slidably seated on an output shaft of the gearbox, where the movable part is connected with the spindle. Movement between the shaft and the sliding part is counteracted by springs. The slidable part is provided with actuating points that may contact switches by axial movements. When a nut on the spindle reaches an end position, a reactive force in the spindle will cause the part to move against the force of springs, eventually actuating a switch and thereby causing interruption of the circuit, thereby protecting motor and engagement between nut and spindle from electric and mechanical overload.